raghav-coder
4/12/2018 - 10:18 AM
AsyncTask
<resources>
<string name="app_name">Github Query</string>
<string name="search">Search</string>
<!--COMPLETED (1) Add a string stating that an error has occurred-->
<string name="error_message">
Failed to get results. Please try again.
</string>
</resources><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.android.datafrominternet.MainActivity">
<EditText
android:id="@+id/et_search_box"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter a query, then click Search"
android:textSize="22sp" />
<TextView
android:id="@+id/tv_url_display"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="Click search and your URL will show up here!"
android:textSize="22sp" />
<!--COMPLETED (2) Wrap the ScrollView in a FrameLayout-->
<!--COMPLETED (3) Make the width and height of the FrameLayout match_parent-->
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp">
<TextView
android:id="@+id/tv_github_search_results_json"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Make a search!"
android:textSize="18sp" />
</ScrollView>
<!--COMPLETED (4) Add a TextView to display an error message-->
<!--COMPLETED (5) Set the text size to 22sp-->
<!--COMPLETED (6) Give the TextView an id of @+id/tv_error_message_display-->
<!--COMPLETED (7) Set the layout_height and layout_width to wrap_content-->
<!--COMPLETED (8) Add 16dp of padding to the error display -->
<!--COMPLETED (9) Use your strings.xml error message to set the text for the error message-->
<!--COMPLETED (10) Set the visibility of the view to invisible-->
<!--COMPLETED (11) Make this TextView a child of the FrameLayout the you added above-->
<TextView
android:id="@+id/tv_error_message_display"
android:textSize="22sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="16dp"
android:text="@string/error_message"
android:visibility="invisible" />
<!-- Add a ProgressBar to indicate loading to your users-->
<!-- Give the ProgressBar an id of @+id/pb_loading_indicator-->
<!-- Set the layout_height and layout_width to 42dp-->
<!--Set the layout_gravity to center-->
<!-- Set the visibility of the ProgressBar to invisible-->
<!-- Make this ProgressBar a child of the FrameLayout that you added above-->
//@@4
<ProgressBar
android:id="@+id/pb_loading_indicator"
android:layout_height="42dp"
android:layout_width="42dp"
android:layout_gravity="center"
android:visibility="invisible" />
</FrameLayout>
</LinearLayout>package com.example.android.datafrominternet;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.example.android.datafrominternet.utilities.NetworkUtils;
import java.io.IOException;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private EditText mSearchBoxEditText;
private TextView mUrlDisplayTextView;
private TextView mSearchResultsTextView;
// Create a variable to store a reference to the error message TextView
private TextView mErrorMessageDisplay;
// Create a ProgressBar variable to store a reference to the ProgressBar
private ProgressBar mLoadingIndicator;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSearchBoxEditText = (EditText) findViewById(R.id.et_search_box);
mUrlDisplayTextView = (TextView) findViewById(R.id.tv_url_display);
mSearchResultsTextView = (TextView) findViewById(R.id.tv_github_search_results_json);
// Get a reference to the error TextView using findViewById
mErrorMessageDisplay = (TextView) findViewById(R.id.tv_error_message_display);
// Get a reference to the ProgressBar using findViewById
mLoadingIndicator = (ProgressBar) findViewById(R.id.pb_loading_indicator);
}
/**
* This method retrieves the search text from the EditText, constructs the
* URL (using {@link NetworkUtils}) for the github repository you'd like to find, displays
* that URL in a TextView, and finally fires off an AsyncTask to perform the GET request using
* our {@link GithubQueryTask}
*/
private void makeGithubSearchQuery() {
String githubQuery = mSearchBoxEditText.getText().toString();
URL githubSearchUrl = NetworkUtils.buildUrl(githubQuery);
mUrlDisplayTextView.setText(githubSearchUrl.toString());
// @@3
new GithubQueryTask().execute(githubSearchUrl);
}
// Create a method called showJsonDataView to show the data and hide the error
/**
* This method will make the View for the JSON data visible and
* hide the error message.
* <p>
* Since it is okay to redundantly set the visibility of a View, we don't
* need to check whether each view is currently visible or invisible.
*/
private void showJsonDataView() {
// First, make sure the error is invisible
mErrorMessageDisplay.setVisibility(View.INVISIBLE);
// Then, make sure the JSON data is visible
mSearchResultsTextView.setVisibility(View.VISIBLE);
}
// Create a method called showErrorMessage to show the error and hide the data
/**
* This method will make the error message visible and hide the JSON
* View.
* <p>
* Since it is okay to redundantly set the visibility of a View, we don't
* need to check whether each view is currently visible or invisible.
*/
private void showErrorMessage() {
// First, hide the currently visible data
mSearchResultsTextView.setVisibility(View.INVISIBLE);
// Then, show the error
mErrorMessageDisplay.setVisibility(View.VISIBLE);
}
// @@1
public class GithubQueryTask extends AsyncTask<URL, Void, String> {
// COMPLETED (26) Override onPreExecute to set the loading indicator to visible
@Override
protected void onPreExecute() {
super.onPreExecute();
mLoadingIndicator.setVisibility(View.VISIBLE);
}
// @@2
@Override
protected String doInBackground(URL... params) {
URL searchUrl = params[0];
String githubSearchResults = null;
try {
githubSearchResults = NetworkUtils.getResponseFromHttpUrl(searchUrl);
} catch (IOException e) {
e.printStackTrace();
}
return githubSearchResults;
}
@Override
protected void onPostExecute(String githubSearchResults) {
// As soon as the loading is complete, hide the loading indicator
mLoadingIndicator.setVisibility(View.INVISIBLE);
if (githubSearchResults != null && !githubSearchResults.equals("")) {
// Call showJsonDataView if we have valid, non-null results
showJsonDataView();
mSearchResultsTextView.setText(githubSearchResults);
} else {
// Call showErrorMessage if the result is null in onPostExecute
showErrorMessage();
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int itemThatWasClickedId = item.getItemId();
if (itemThatWasClickedId == R.id.action_search) {
makeGithubSearchQuery();
return true;
}
return super.onOptionsItemSelected(item);
}
}
## Steps to use Async Task
1. Create a inner class GithubQueryTask inside MainActivity that extends AsyncTask
2. Override doInBackground and onPostExecute
3. Instantiate an object of GithubQueryTask and call execute passing in the URL
4. Add a Porgress Indicator